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Deeply Sub-Wavelength Non-Contact Optical Metrology of Sub-Wavelength Objects

Deeply Sub-Wavelength Non-Contact Optical Metrology of Sub-Wavelength Objects
Deeply Sub-Wavelength Non-Contact Optical Metrology of Sub-Wavelength Objects

Microscopes and various forms of interferometers have been used for decades in optical metrology of objects that are typically larger than the wavelength of light λ. Metrology of sub-wavelength objects, however, was deemed impossible due to the diffraction limit. We report the measurement of the physical size of sub-wavelength objects with deeply sub-wavelength accuracy by analyzing the diffraction pattern of coherent light scattered by the objects with deep learning enabled analysis. With a 633 nm laser, we show that the width of sub-wavelength slits in an opaque screen can be measured with an accuracy of ∼λ/130 for a single-shot measurement or ∼λ/260 (i.e., 2.4 nm) when combining measurements of diffraction patterns at different distances from the object, thus challenging the accuracy of scanning electron microscopy and ion beam lithography. In numerical experiments, we show that the technique could reach an accuracy beyond λ/1000. It is suitable for high-rate non-contact measurements of nanometric sizes of randomly positioned objects in smart manufacturing applications with integrated metrology and processing tools.

0003-6951
Rendon-Barraza, Carolina
8330193a-4b7d-45c8-8427-20de72e861b8
Aik Chan, Eng
803a26e6-c74c-47fe-943b-80f790955e3b
Yuan, Guanghui
d7af6f06-7da9-41ef-b7f9-cfe09e55fcaa
Adamo, Giorgio
8c4da92b-f849-42d4-99c8-b0eb4ba1c73a
Pu, Tanchao
89eb5a37-31bf-469a-ae29-c871d5d25c65
Zheludev, Nikolai
32fb6af7-97e4-4d11-bca6-805745e40cc6
Rendon-Barraza, Carolina
8330193a-4b7d-45c8-8427-20de72e861b8
Aik Chan, Eng
803a26e6-c74c-47fe-943b-80f790955e3b
Yuan, Guanghui
d7af6f06-7da9-41ef-b7f9-cfe09e55fcaa
Adamo, Giorgio
8c4da92b-f849-42d4-99c8-b0eb4ba1c73a
Pu, Tanchao
89eb5a37-31bf-469a-ae29-c871d5d25c65
Zheludev, Nikolai
32fb6af7-97e4-4d11-bca6-805745e40cc6

Rendon-Barraza, Carolina, Aik Chan, Eng, Yuan, Guanghui, Adamo, Giorgio, Pu, Tanchao and Zheludev, Nikolai (2021) Deeply Sub-Wavelength Non-Contact Optical Metrology of Sub-Wavelength Objects. Applied Physics Letters, 6 (6), [066107]. (doi:10.1063/5.0048139).

Record type: Article

Abstract

Microscopes and various forms of interferometers have been used for decades in optical metrology of objects that are typically larger than the wavelength of light λ. Metrology of sub-wavelength objects, however, was deemed impossible due to the diffraction limit. We report the measurement of the physical size of sub-wavelength objects with deeply sub-wavelength accuracy by analyzing the diffraction pattern of coherent light scattered by the objects with deep learning enabled analysis. With a 633 nm laser, we show that the width of sub-wavelength slits in an opaque screen can be measured with an accuracy of ∼λ/130 for a single-shot measurement or ∼λ/260 (i.e., 2.4 nm) when combining measurements of diffraction patterns at different distances from the object, thus challenging the accuracy of scanning electron microscopy and ion beam lithography. In numerical experiments, we show that the technique could reach an accuracy beyond λ/1000. It is suitable for high-rate non-contact measurements of nanometric sizes of randomly positioned objects in smart manufacturing applications with integrated metrology and processing tools.

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More information

Published date: 23 June 2021

Identifiers

Local EPrints ID: 449934
URI: http://eprints.soton.ac.uk/id/eprint/449934
ISSN: 0003-6951
PURE UUID: 650831a7-9f52-4bbc-b58d-4314519d0473
ORCID for Tanchao Pu: ORCID iD orcid.org/0000-0002-1782-5653
ORCID for Nikolai Zheludev: ORCID iD orcid.org/0000-0002-1013-6636

Catalogue record

Date deposited: 28 Jun 2021 16:30
Last modified: 26 Nov 2021 03:24

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Contributors

Author: Carolina Rendon-Barraza
Author: Eng Aik Chan
Author: Guanghui Yuan
Author: Giorgio Adamo
Author: Tanchao Pu ORCID iD

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